I don't think I've ever visited a place in the U.S. where I didn't see chipmunks (I found the little guy above in Bryce Canyon Utah). That's probably because there are 25 species of chipmunks and only one of those species is found outside of North America (the Siberian chipmunk, but it's not just found in Siberia...) Unlike their grey squirrel cousins, chipmunks are ground-dwelling squirrels that live in burrows. We're not seeing many chipmunks this time of year, but come spring they'll be active again, collecting food and getting ready for mating season in late spring and fall. They're omnivores and "crepuscular," which means they're most active at dusk and dawn.
I've noticed that chipmunks make little sounds whenever I see them, so I did a little checking. It seems that, like birds, they use different vocalizations at different times. Check out this research:
Want to learn more about chipmunks? Check out this earlier post!